Recently, as an environmentally-friendly vehicle, attention has been drawn to an electrically-driven vehicle which is equipped with an electrical storage device (such as, for example, a secondary battery and a capacitor) and which drives using a driving force generated from electric power stored in the electrical storage device. The electrically-driven vehicle includes, for example, an electric vehicle, a hybrid vehicle, a fuel-cell vehicle, or the like.
The electrically-driven vehicle is provided, in some cases, with a motor generator which generates the driving force for driving in response to the electric power from the electrical storage device upon departure and acceleration, and which generates electricity due to regenerative braking upon braking and stores electrical energy in the electrical storage device. As described above, the electrically-driven vehicle is equipped with an inverter in order to control the motor generator in accordance with a travelling state.
The vehicle as described above is provided, in some cases, with a voltage converting apparatus (or a converter) between the electrical storage device and the inverter in order to stably supply electric power which is used by the inverter and which varies depending on a vehicle state. The converter sets input voltage of the inverter to be higher than output voltage of the electrical storage device, thereby allowing high output of a motor. The converter also reduces a motor current in the same output, thereby reducing the size and cost of the inverter and the motor.
For further improvement of fuel efficiency of the electrically-driven vehicle, it is important to reduce a loss of the converter and to improve efficiency. Thus, for example, Patent documents 1 to 3 have proposed a technology of switching-driving a boost converter using one arm. According to such a technology, it is considered that the loss of the converter can be reduced by an amount of reduction in current ripple.